The objectives of this work are to characterize the process of viral mRNA biogenesis and its control in cells infected with herpes simplex virus 1 (HSV-1). Specifically this includes characterization of 1) the size, genome locations and organization of viral transcription units, 2) the size, structure, polypeptide coding, and genome mapping of the viral mRNAs, and 3) the processing of the primary viral transcripts. The goals for the coming year are: a) Characterization of delayed-early (DE) mRNAs. By using drugs and temperature sensitive mutants to restrict transcription to early genes, we will identify and separate DE mRNAs by hybridization to HSV-DNA cellulose and by electrophoresis in gradient, denaturing gels. The isolated RNAs will be characterized by in vitro translation and by Southern blot and R-loop mapping techniques. b) UV mapping of early viral mRNAs. The sensitivity of synthesis of individual mRNAs to UV irradiation of the infecting virus or the infected cell will be studied. This will provide data on the early viral transcription units and information on possible cotranscriptions of viral genes. c) Processing of viral primary transcripts will be investigated by two approaches. The first will consist of selective enzymatic digestion of hybrids formed between unlabeled mRNAs and labeled restriction fragments of viral DNA followed by electrophoretic analysis of the products in neutral and alkaline gels (Berk and Sharp technique). The second will be "R-loop" mapping of mRNA and HSV-1 DNA restriction fragments by electron microscopy.